1. Field of the Invention
The present invention relates, in general, to a catalyst for the polymerization of olefins, superior in various properties and a method for the preparation of the same. Particularly, the present invention relates to a catalyst capable of providing high stereoregularity to polymers or copolymers when they polymerized from .alpha.-olefins containing at least 3 carbon atoms by use of the catalyst, and a method for the preparation of the same.
2. Description of the Prior Art
Conventionally, catalysts for polymerizing olefins have been prepared from magnesium compounds and electron donors in combination with aids, such as titanium compounds, organoaluminum compounds and silicon compounds by various methods.
Japanese Laid-Open Publication Patent No. 40293/79 proposes a method for preparing a solid titanium catalyst comprising of magnesium, titanium, halogen and an electron donor, saying that a compound by a general formula, Ti(OR.sup.2).sub.4 wherein R.sup.2 is a C.sub.1 .about.C.sub.10 alkyl, aryl or cycloalkyl and a compound represented by a general formula, Mg(OR.sub.1).sub.2 -.sub.n X.sub.n wherein R.sub.1 is a C.sub.1 .about.C.sub.10 alkyl; aryl or cycloalkyl, X is a halogen and 0&lt;n&gt;2 both are used along with an electron donor. The solid titanium catalyst of the cited reference is prepared by forming a homogeneous solution of the three compounds mentioned, applying precipitation treatment to the homogeneous solution, to give a solid composition comprising magnesium, titanium and the electron donor, and contacting the composition with a titanium compound in liquid state. The precipitation treatment according to this method can be carried out by lowering the concentration of the homogeneous solution or by adding to the homogeneous solution a non-solvent for the solid ingredient to be precipitated or a recrystalline compound, such as a halogen compound of silicon or tin.
In addition, there have been disclosed a method for the preparation of solid titanium catalyst, comprising dissolving in various alcohols a magnesium compound keeping its central metal in an oxidation state of divalent in a non-active hydrocarbon solvent, to give a homogeneous solution, contacting the homogeneous solution with an electron donor, and further contacting this complex homogeneous solution with a titanium compound (see Japanese Patent No. Sho. 63-54004 and U.S. Pat. No. 4,330,649).
As mentioned above, the conventional olefins preparation methods show a disadvantage in that a step of precipitating the solid composition has to be carried out in advance of contacting the solid composition with the titanium compound. In addition, since the properties of the catalysts prepared by the conventional methods are greatly varied in dependence on the intermixing process of the constituents for catalysts, combination of the preparing stages used, and difference of the conditions employed in the process and the combination, it is impossible to convince that similar results are obtained when the catalysts are prepared under a given condition by the conventional methods. Accordingly, there is another drawback that the conventional catalysts could have extremely poor properties and capabilities.